The identity and function of immune cells is determined in part by their gene expression profiles. These are controlled by a number of transcriptional regulators that include transcription factors, chromatin modifiers and others. Each regulator controls the expression of a number of target genes and each gene is regulated by a number of regulators. Some of the target genes are regulators themeselves, creating a regulatory structured known as transcriptional regulatory network or gene regulatory network. We combine computational methods with high-throughput gene expression data from single cells to reconstruct the transcriptional regulatory networks controlling the identity and function of immune cells.